The present invention relates to an optical recording method and an apparatus using the method, and in particular, to an optical recording method and an apparatus using the method suitable for utilizing an optical recording medium in which a signal is recorded according to a fact that when a light spot is radiated on a location of the optical recording medium, an optical characteristic of the medium changed because the temperature at the location is increased.
As described in the JP-A- No. 59-68844, an apparatus in which a laser light is collected to form a laser beam having a very small diameter of about 1 .mu.m and is radiated, for example, onto a rotating optical recording disk coated with a photosensitive recording material so as to record signals at a high density and to reproduce the recorded signals has such advantages that due to a high recording density, the memory cost per bit can be lowered, that a high-speed access is possible, and that the optical head and the optical recording disk are not brought into contact with each other during the recording and playback operations and hence the reliability of the optical recording disk and the optical recording apparatus can be improved, and therefore the apparatus has been considered to provide new recording apparatus and medium to the information-oriented society in the future.
As recording media applicable to the optical recording, there have been proposed, for example, a medium having a thin recording film which is evaporated by the thermal energy of a laser light to form small holes in the thin film and a medium having a thin recording film of which the optical density is changed by use of the thermal energy of a laser light.
In addition, for the recording thin film in which the optical density is changed, it has been reported that the optical density can be reversibly changed by use of an amorphous thin film. The fact that the optical density can be reversibly changed means that a signal can be recorded, reproduced, and erased; however, the recording thin film made of an amorphous material is substantially unstable, namely, the crystallization of the amorphous material proceeds also in the room temperature and hence such a thin film is not suitable for storing the recorded data for a long period of time. Moreover, Te, Se, and Sn are used to increase the recording sensitivity; however, these materials have a harmful influence on a human body, and when the thin film is manufactured conducted, there is a possibility that a problem of contamination may arise. In addition, the high recording sensitivity means that the thin film is susceptible to influences of the temperature, light, and the like, which leads to a problem of retension for keeping the recorded data.
As an optical recording medium, an alloy has been developed in which a phase change is effected between two different crystal states and the information recording and erasure can be achieved by use of the difference of optical reflection factor between these crystals. This alloy is described in the JP-A- No. 60-186825 and JP-A- No. 61-9542.
For the recording media capable of a high-density recording, a high-speed recording function is especially required to record the increasing amount of information.